1. Technical Field
The present invention relates to a positioning table, for example, for positioning the mask of exposing devices in manufacturing semiconductors, the positioning to be done on a plane, and provides a positioning table which is low in total height, has high rigidity, and which permits exact positioning to be done, involving small backlash, and rotational movement to be made, with an arbitrary point on the movable table as the center of rotation.
2. Prior Art
The conventional positioning table is composed, particularly as shown in FIG. 1, of an x-table 2 having an x-direction straight-line guide 1, a y-table 4 having a y-direction straight-line guide 3 on the x-table 2, and a rotary table 6 having a rotary shaft 5 placed on the y-table, said tables being piled one upon another, with the movement in the x-direction provided by the drive of a motor 8 fixed on a base 7, the movement in the y-direction provided by the drive of a motor 9 fixed on the x-table, and the rotational movement provided by the drive of a motor fixed on the y-table 4.
In the aforementioned construction, the x-table 2 and the y-table 4 which move in two criss-crossing directions are piled one upon another and on them, the rotary table 6 is further superposed, thereby providing a triple stacked construction. Consequently, the total height of the positioning table is high and its rigidity low. Besides, since the rotary shaft 5 of the rotary table 6 was secured in a set position on the y-table 4, it was impossible to make the rotational movement, with an arbitrary position on the y-table 4 as the center of rotation. Further, large bearing friction in the straight line movements and the rotational movement result in large backlash, giving rise difficulty in positioning.